Method for fabricating a half-tone type phase shift mask

Abstract

A method is disclosed for the fabrication of a phase shift mask comprising the steps of: forming chrome patterns on a transparent substrate; coating a phase shift layer and a negative photosensitive film on the entire area of the resulting structure, in sequence; exposing the photosensitive film to a light incident from the backside of the transparent substrate with the chrome patterns serving as a mask and developing the illuminated area of the photosensitive film, to form photosensitive film patterns; etching the phase shift layer to form phase shift patterns which are each positioned between the chrome patterns, with the photosensitive film patterns serving as a mask; subjecting the chrome patterns to wet etching, to conduct etching at the upper surface and the opposite edges of the chrome patterns so that each of the chrome patterns are spaced from each of the phase shift patterns; and removing the photosensitive film patterns with the transparent substrate exposed through the spaces between the etched chrome patterns and the phase shift patterns. The present method is advantageous in that a conventional chrome mask is utilized, so that particular equipments and additional designing are not necessary while the production cost thereof is reduced. In addition, the method is superior to conventional ones in process capability, thereby increasing the production yield of the devices.

What is claimed is: 
     
       1. A method for the fabrication of a phase shift mask, comprising the steps of: forming chrome patterns on a transparent substrate;   coating a phase shift layer and a negative photosensitive film on the entire area of the resulting structure, in sequence;   exposing the photosensitive film to a light incident from the backside of the transparent substrate with the chrome patterns serving as a mask and developing the photosensitive film, to form photosensitive film patterns on the phase shift layer;   etching the phase shift layer to form phase shift patterns which are each positioned between the chrome patterns, with the photosensitive film patterns serving as a mask;   subjecting the chrome patterns to wet etching, to conduct etching at the upper surface and the opposite edges of the chrome patterns so that each of the chrome patterns are spaced from each of the phase shift patterns; and   removing the photosensitive film patterns, whereby a portion of the transparent substrate is exposed through the spaces between the etched chrome patterns and the phase shift patterns.   
     
     
       2. A method in accordance with claim 1, wherein said chrome patterns are formed so thick that they can sufficiently screen light after said wet etching. 
     
     
       3. A method according to claim 1, wherein the chrome patterns are formed directly onto the transparent substrate. 
     
     
       4. A method according to claim 3, wherein the transparent substrate forms a lowermost base layer of the phase shift mask. 
     
     
       5. A method for the fabrication of a phase shift mask, comprising the steps of: forming chrome patterns distant from each other over a transparent substrate;   coating a phase shift layer and a negative photosensitive film over the entire area of the resulting structure, in sequence;   exposing the photosensitive film to a light incident from the backside of the transparent substrate for a short time to expose only a portion of the photosensitive film in the exposure region, with the chrome patterns serving as a mask;   developing the illuminated area of the photosensitive film, to form phase shift layer and photosensive film patterns which are narrower than the distance between the chrome patterns;   etching the phase shift layer to form phase shift patterns which are each spaced from each of the chrome patterns with the photosensitive film patterns serving as a mask; and   removing the photosensitive film patterns whereby a portion of the transparent substrate is exposed through the spaces between the chrome patterns and the phase shift patterns.   
     
     
       6. A method according to claim 5, wherein the transparent substrate comprises a lowermost layer and wherein the chrome patterns are formed directly on the transparent substrate.